Temperature effects on the hyperfine coupling constants (hfcc's) of the methyl radical have been investigated by means of direct ab initio molecular dynamics (MD) method. The calculations showed that the hydrogen-hfcc (H-hfcc) of CH increases with increasing temperature. Also, it was indicated that hfcc of the carbon atom of CH3 increases as temperature is increased. The H-hfcc's of CH3 were varied from -22.94 to -22.77 G in the temperature ranges 10-300 K. These features were in good agreement with electron paramagnetic resonance (EPR) experiments. The effects of temperature on H-hfcc were discussed on the basis of theoretical results.